In the field of printing, the most common type of printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical-type system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a very short, precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the armature or plunger normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that specific area between the solenoids and the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are positioned in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower or smaller print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer which is utilized for receipt and journal printing operation, the print head structure may be a multiple element type and horizontally disposed with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner across the receipt or journal paper and wherein the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head. In the wire matrix printer which is utilized for business forms or like record media printing operation, the print head may be oriented in a manner wherein the nose is pointed downward for printing on the form or record media while the carriage and print head are moved above and across the form or media in the horizontal direction.
Further, the printer structure may be an arrangement which includes a plurality of equally-spaced, horizontally-aligned, single element print heads which are caused to be moved in back and forth manner to print successive lines of dots in making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing. These single wire actuators or solenoids are generally tubular or cylindrically shaped and include a shell which encloses a coil, an armature and a resilient member arranged in manner and form wherein the actuator is operable to cause the print wire to be axially moved a small precise distance in dot matrix printing.
In the case of a wire matrix printer which is utilized for form or multi-copy printing, the difference in thickness of the forms or copies may require some means or mechanism for adjusting the gap or the distance between the print head and the printer platen. It is in the field of printers and more specifically in the field of dot matrix printers for use in cash registers or like register machines that the subject matter of the present invention is most closely associated and which invention provides for improved and advantageous positioning and control of the gap or distance between the print head and the printer platen.
Conventionally, an ink ribbon has been incorporated in the mechanism of a dot matrix printer which ribbon is caused to be positioned by guiding and/or driving same in the area between the print head and the paper or like record media for the purpose of transferring ink onto the paper from the ink ribbon during printing operation. Further, it is known that the dot matrix printer mechanism for a cash register is constructed so that the platen is moved away from the print head when paper is inserted into the printer.
However, in such a conventional dot matrix printer, the use of an ink ribbon and the associated containing, guiding, and driving means can become complicated in providing the required transfer of ink from the ribbon to the paper. It is further noted that the printer that is utilized for cash registers or like machines should be compact in nature along with a reduced platen size and a reduction in width of the printer, thus permitting a lesser distance of print head travel in the longitudinal direction of the platen.
Representative documentation in the field of wire matrix print heads includes U.S. Pat. No. 3,960,256, issued to C. Bickoff et al. on June 1, 1976, which discloses an adjustable carriage apparatus wherein the print head is secured to a carriage whose position may be adjusted with respect to the paper by rotating a pair of bearings.
U.S. Pat. No. 4,086,997, issued to E. S. Wu on May 2, 1978, discloses an adjustable support for a print head assembly which changes the spacing between the print head and the paper supporting surface to accommodate multiple sheets of paper and to facilitate changing of paper and ribbon.
U.S. Pat. No. 4,088,215, issued to L. Bader on May 9, 1978, discloses record media compensation means including a motor for positioning a printer frame for locating the print head at a proper distance from the record media.
U.S. Pat. No. 4,090,600, issued to H. H. Biedermann on May 23, 1978, discloses a printing device having a fixed guide bar supporting a flexible strip which serves to press the paper against the platen and serves as a track for print head guide rollers. The guide bar guides paper insertion and provides a camming surface to rock the ribbon cassette upon traversal of the print head.
U.S. Pat. No. 4,165,188, issued to W. D. Rempel on Aug. 21, 1979, discloses a ribbon mask and guide carried with the print head and positioned between the print ribbon and the printing surface and the mask has an oval opening for the print wires.
U.S. Pat. No. 4,243,331, issued to J. G. Savage et al. on Jan. 6, 1981, discloses apparatus for adjusting a carriage relative to a platen including support rails, a tubular housing and a C-shaped member supported from the support rails for pivotal and translational movement.
U.S. Pat. No. 4,383,775, issued to K. L. Trammell et al. on May 17, 1983, discloses a ribbon shield for use with a cassette which snaps into the front of the cassette to cover an exposed portion of ribbon. The shield has a central aperture for the ribbon to pass through it and a curved portion to accommodate paper motion past the cassette.
U.S. Pat. No. 4,420,269, issued to R. Ackermann et al. on Dec. 13, 1983, discloses a device for lifting the printing head off the platen which includes means for changing the distance between the print element and the platen an amount to facilitate paper feeding and an additional amount for paper insertion.
U.S. Pat. No. 4,483,633, issued to J. J. Kosner et al. on Nov. 20, 1984, discloses a matrix print head printer wherein back-up platen rollers are moved from a first position adjacent the print head when actuated to a second position distal from the print head when the print head is not actuated. The printer also includes an ink source comprising an endless ink ribbon and an ink guard disposed between the ribbon and the document path with apertures in the guard for printing operation.
U.S. Pat. No. 4,492,484, issued to H. Akazawa et al. on Jan. 8, 1985, discloses a ribbon mask and guide for wire dot printers wherein a carriage supported print head includes a nose member on first and second holding members disposed on the carriage and the ribbon mask is removably held between first and second members.
U.S. Pat. No. 4,493,566, issued to R. G. McMahon et al. on Jan. 15, 1985, discloses a front to back adjustment for a carriage assembly which has first and second parallel supports, a pulley support assembly on one support, and a bearing assembly on the other support.
And, U.S. Pat. No. 4,496,256, issued to H. L. McMorrow et al. on Jan. 29, 1985, discloses an impact printing apparatus which has a ribbon mask angled at either side of the print head and a slot in the mask extends at an angle so that the slot ends do not engage the paper being printed.